Hull for propeller-driven vessels

ABSTRACT

A hull for propeller-driven vessels includes a front portion and a rear portion. The rear portion includes a leading section and a trailing section. It further includes a hull plating having at opposite sides of the rear portion mutually inclined outer guide surface means constructed and arranged to effect in the region of the leading section a rearward and upward deflection of fluid streaming along the hull towards the rear portion. An elongated rearwardly tapering bulge extends rearwardly from the region of the leading section of the rear portion.

United States Patent Herbert Schneekluth Aachen, Germany Aug. 9, 1968 Mar. 2, 1971 [73] Assignee Blohm & Voss A G Hamburg, Germany [32] Priority Aug. 11, 1967 [33] Germany [72] Inventor [21 App]. No. [22] Filed [45] Patented [54] HULL FOR PROPELLER-DRIVEN VESSELS 6 Claims, 2 Drawing Figs.

[52] US. Cl. 114/57 [51] Int. Cl. B63b l/04 [50] Field of Search 114/57, 56

[56] References Cited UNITED STATES PATENTS 538,353 4/1895 Schermerhorn 2,564,560 8/ l 951 Carlotti 3,162,168 12/1964 Ferris et a] F ORElGN PATENTS 7/1923 Great Britain OTHER REFERENCES Vol. 11, Pages 519 & 520, Hydrodynamics in Ship Design Published by The Society of Naval Architects and Marine Engineers, New York, 6, NY. Vol. II, 1957.

Primary Examiner-Andrew H. Farrell Attorney-Michael S. Striker ABSTRACT: A hull for propeller-driven vessels includes a front portion and a rear portion. The rear portion includes a leading section and a trailing section. It further includes a hull plating having at opposite sides of the rear portion mutually inclined outer guide surface means constructed and arranged to effect in the region of the leading section a rearward and upward deflection of fluid streaming along the hull towards the rear portion. An elongated rearwardly tapering bulge extends rearwardly from the region of the leading section of the rear portion.

ll-IULL FOR PROPELLER-DRIVEN VESSELS BACKGROUND OF THE INVENTION The present invention generally relates to propeller-driven vessels, and more particularly to hulls for propeller-driven vessels.

Conventional hulls of propeller-driven vessels, that is to say ships, are produced with strake lines. A strake is one breadth of planks forming a continuous strip on the bottom or the sides of a vessel and reaching from the stem to the stern of the same. In vessels so constructed it has been proposed to provided stern bulges, that is a bulge-shaped portion of the hull located at the stern which serves the purpose of regulating the flowstream pattern so as to reduce periodic changes in the flow delivery direction of the rotating propeller blades, and the resulting vibrations. Beyond this purpose, however, stern bulges in vessels having strake-lined hulls provide no advantages; in particular, they do not afford a significant reduction in drag resistance and a concomitant saving of drivepower requirements, even if some improvement in the flow is produced by the provision of such a stern bulge.

I have found, however, that this is different if a stern bulge is provided in a vessel which does not have strake lines, that is wherein the outer surfaces bounding thehull consist of flat plates. The provision of a stern bulge under these circumstances creates special hydrodynamicconditions which result in a significant saving in drive-power requirements for such a vessel.

It is accordingly an object of the present invention to provide a hull construction having a reduced drag-resistance factor.

A concomitant object of the invention is to provide such a hull construction which, owing to its novel configuration, permits significant savings in drive-power requirements.

SUMMARY OF THE INVENTION In accordance with the above requirements and others which will become apparent hereafter, I provide a hull for propeller-driven vessels which comprises a front portion, and a rear portion. The front portion includes a leading section which is closer to and a trailing section which is farther spaced from the front portion. Further, the rear portion includes a hull plating having at opposite sides of the rear portion mutually. inclined outer guide surface means which are constructed and arranged so as to effect in the region of the leading section of the rear portion a rearward and upward deflection of fluid which streams along the hull from the front portion thereof towards the rear portion. In accordance with my invention I provide an elongated rearwardly tapering bulge which extends from the rear portion and which merges into the same in the region of the leading section thereof.

By resorting to my invention I prevent or counteract separation or breakup of the flow stream, as seen with respect to the width of the ships bull, in the region of the stern bulge, and this in turn results in a reduction of the hull drag resistance. This enables me to obtain a reduction in drive-power requirements for a vessel hull so constructed.

Additionally, another saving of drive power is afforded by the fact that my novel construction assures that a substantially greater part of the boundary layer of the hull of the ship, that is the boundary layer of fluid streaming along the hull, will pass through the cross section of the rotating propeller than has been known heretofore. This makes possible, as is well known, the partial recovery of losses resulting from viscosity resistance. By keeping the area of attachment of the bulge to the bottom of the hull comparatively wide, I further increase the guide-surface effect of the bulge.

Again, I can still further improve the guide-surface effect of the bulge by providing a longitudinal fin member, a so-called dead fin, which may be located either wholly or partly above or below the bulge, or which may be located both above and below the bulge. Such a dead fin may be widened out in the forward direction of the hull. In accordance with my invention the bulge may have an asymmetrical cross-sectional configuration such that, if one divides the bulge by an imaginary vertical plane bisecting the bulge in longitudinal direction of the same, the bulge will have two differently dimensioned parts located at opposite sides of this plane. This a oids the disadvantages of asymmetrical operation of the propeller.

To facilitate manufacture of the bulge a preferred embodiment of my invention suggests that the bulge be bounded by an outer circumferential surface which is developable, or that it be assembled from components, such as plates, which have outer surfaces some of which are developable and some of which are planar. This makes for a particularly simple and inexpensive manufacture of the bulgemember.

Finally, I may also provide a cylindrical or conical intermediate member which is located intermediate the trailing end of the bulge and the propeller. Of course, the propeller may be mounted directly on the trailing end of the bulge, by providing the intermediate member "I effect a more strong reduction in the drag than in the flow stream factor, and a concomitant improvement in the hydrodynamic factor of the hull. This applies, incidentally,even in ships wherein the form of the stem is different from the type here under discussion.

The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a diagrammatic side view illustrating a first embodiment of the invention; and

FIG. 2 is a view similar to FIG. 1, but illustrating a second embodiment of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Discussing now the drawing in detail, and firstly FIG. 1 thereof, it will be seen that I have illustrated the stern or that portion 1 of a ship hull the remainder including the front portion of which is not shown because it is not of importance in connection with the present invention. However, the front portion must of course be understood to be located toward the right of stern l in FIG. I. As shown, the stern 1 has a flat outer skin structure, that is the hull plating la does not have strake lines and is rather provided with flat outer guide surfaces lb which are mutually inclined at opposite sides of the stem 1 and a bottom face having a substantially horizontal general plane and facing downwardly. The trailing section of the stem 1 is identified by reference character A whereas the leading section is identified by reference character B. During forward movement of a vessel provided with such a hull the fluid boundary layer flowing rearwardly along the hull, that is inthe direction towards the trailing section A from the right-hand side of the drawing, will be sharply deflected in rearward and upward direction at the forward section of the stern, that is at the upwardly inclined line constituting the forward section and identified with reference character B.

In accordance with my present invention the stem 1 is provided with a stern bulge or propeller mount 2 which is elongated and tapers rearwardly from the forward section B in the direction towards the rearward section A. The stem bulge 2 merges with the forward section B at the widest portion of the bulge 2, which latter in the illustrated embodiment is of cone shape, and thus has a developable outer circumferential surface, in the region of the section B, as indicated by the arrows 2. In other words, the, base part or root indicated by the arrows 2 extends rearwardly from the forward section B at or in the region of which the fluid stream is deflected rearwardly and upwardly. This particular juncture of the base or root 2" of the bulge 2 with the stem 1 at or in the region where the deflection of the fluid stream normally takes place assures the aforementioned improvement of the hydrodynamic factor of the ship and the strong reduction in drag by providing the boundary layer towards propeller 3, and accordingly reduces significantly the drive-power requirement necessary for propelling such a vessel through a liquid.

In the embodiment of FIG. 1 the propeller 3 with the propeller cap 6 is carried directly by the trailing end of the stern bulge 2. A dead fin 4 of known construction is also provided extending from the upper side of the stern bulge 2 to the stem 1; this dead fin 4 improves the flow of liquid in the direction towards the propeller 3 and prevents or counteracts break up or separation of the flow between the bulge and the underside of the stern located above the bulge.

The embodiment of FIG. 2 is substantially the same as that of FIG. 1. Identical reference numerals have been used to identify identical components. Unlike the embodiment of FIG. 1, however, the embodiment of FIG. 2 shows an intermediate member 5 interposed between the propeller 3 and the trailing end 2 inches of the stern bulge 2. This intermediate member 5 may be cylindrical or conical in cross-sectional configuration and can be used to advantage with certain stern shapes. As pointed out earlier, its use will further reduce the drag by an extent greater than the reduction in the flow stream factor, and the use of the intermediate member 5 is possible with advantage with hulls having various different stern forms.

The cross-sectional configuration of the stern bulge 2 need not be symmetrical. In fact, it may be asymmetrical, which is to say that if the stern bulge 2 is assumed to be bisected by a vertical plane in the direction of elongation of the stern bulge 2, the cross-sectional configuration of the two sections of the bulge located at opposite sides of this plane may be different. While such an arrangement is not shown in detail, being clearly evident to those having ordinary skill in the art, it is pointed out that it will serve to counteract the disadvantages resulting from asymmetrical operation of the propeller 3.

It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of constructions differing from the types described above.

While the invention has been illustrated and described as embodied in a hull for propeller-driven vessels, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can by applying current knowledge readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention and, therefore. such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the following claims.

I claim:

1. A hull for propeller-driven vessels, comprising a bow portion, and a stern portion including a leading section closer to and a trailing section farther from said bow portion, said stern portion further including hull plating having at opposite sides of said stern portion mutually inclined outer guide surface means constructed and arranged so as to effect in the region of said leading section a rearward and upward deflection of fluid which streams along said hull from said bow portion towards said stern portion; an elongated rearwardly tapering propeller mount including a main mount portion extending from said stern portion and merging into the same in said region of said leading section, an aft mount portion and an intermediate mount portion of substantially cylindrical configuration extending rearwardly from said main mount portion between the same and said aft mount portion; and a propeller mounted on said intermediate mount portion.

2. A hull for propeller-driven vessels, comprising a bow portion, anda stern portion including a leading section closer to and a trailing section farther from said bow portion, said stern portion further including hull plating having at opposite sides of said stern portion mutually inclined outer guide surface means constructed and arranged so as to effect in the region of said leading section a rearward and upward deflection of fluid which streams along said hull from said bow portion towards said stern portion; an elongated rearwardly tapering propeller mount including a main mount portion extending from said stern portion and merging into the same in said region of said leading section, an aft mount portion and an intermediate mount portion of substantially conical configuration extending rearwardly from said mount portion between the same and said aft mount portion; and a propeller mounted on said intermediate mount portion.

3. A hull as defined in claim 2, said mount having an upper side and a lower side; and further comprising a dead fin ex tending at least at one side of said mount in direction from said bow portion towards'said stern portion.

4. A hull as defined in claim 3, wherein said dead fin extends at said upper side of said mount.

5. A hull as defined in claim 3, wherein said dead fin is substantially coextensive with said mount in the longitudinal direction of the latter.

6. A hull as defined in claim 2, said amount being bounded by a developable outersurface. 

1. A hull for propeller-driven vessels, comprising a bow portion, and a stern portion including a leading section closer to and a trailing section farther from said bow portion, said stern portion further including hull plating having at opposite sides of said stern portion mutually inclined outer guide surface means constructed and arranged so as to effect in the region of said leading section a rearward and upward deflection of fluid which streams along said hull from said bow portion towards said stern portion; an elongated rearwardly tapering propeller mount including a main mount portion extending from said stern portion and merging into the same in said region of said leading section, an aft mount portion and an intermediate mount portion of substantially cylindrical configuration extending rearwardly from said main mount portion between the same and said aft mount portion; and a propeller mounted on said intermediate mount portion.
 2. A hull for propeller-driven vessels, comprising a bow portion, and a stern portion including a leading section closer to and a trailing section farther from said bow portion, said stern portion further including hull plating having at opposite sides of said stern portion mutually inclined outer guide surface means constructed and arranged so as to effect in the region of said leading section a rearward and upward deflection of fluid which streams along said hull from said bow portion towards said stern portion; an elongated rearwardly tapering propeller mount including a main mount portion extending from said stern portion and merging into the same in said region of said leading section, an aft mount portion and an intermediate mount portion of substantially conical configuration extending rearwardly from said mount portion between the same and said aft mount portion; and a propeller mounted on said intermediate mount portion.
 3. A hull as defined in claim 2, said mount having an upper side and a lower side; and further comprising a dead fin extending at least at one side of said mount in direction from said bow portion towards said stern portion.
 4. A hull as defined in claim 3, wherein said dead fin extends at said upper side of said mount.
 5. A hull as defined in claim 3, wherein said dead fin is substantially coextensive with said mount in the longitudinal direction of the latter.
 6. A hull as defined in claim 2, said amount being bounded by a developable outer surface. 